It is known in sail boats to attach a light weight strip of fabric to a sail boat sail to form a tell-tale that will flutter in the wind and thereby provide the crew with an indication of the airflow over the sail so that sail can be trimmed to maximize the performance of the boat. However, at night or in low light conditions these tell-tales are difficult to see. Therefore it is known to use a flashlight to view the tell-tale, or to mount a light source on the mast to shine on the tell-tale. Furthermore, U.S. Pat. No. 5,477,424 proposes fashioning a tell-tale of an optical fiber ribbon that is housed between transparent or translucent plastic straps and receives light from an LED communicating with the end of the optical fiber ribbon so that light emits along its length to make the tell-tale visible at night.